Field
The present invention relates generally to sputtering systems, and more specifically to pulsed DC sputtering.
Background
Sputtering historically includes generating a magnetic field in a vacuum chamber and causing a plasma beam in the chamber to strike a sacrificial target, thereby causing the target to sputter (eject) material, which is then deposited as a thin film layer on a substrate, sometimes after reacting with a process gas. Sputtering sources may employ magnetrons that utilize strong electric and magnetic fields to confine charged plasma particles close to the surface of the target. An anode is generally provided to collect electrons from the plasma to maintain plasma neutrality as ions leave to bombard the target.
The industry has evolved over the years in various attempts to maximize sputtering efficiency, decrease power consumption requirements, minimize the heat load of the system, minimize arcing and/or increase the types of substrates that may be used in the system.
Moreover, sputtering a thin film of, for example, titanium dioxide (TiO2) or silicon dioxide (SiO2) onto a polyethylene substrate presents unique challenges in the industry because polyethylene is a plastic with a low melting point or low heat tolerance. Currently-available sputtering systems, whether DC or AC type systems, require a high heat load to effectuate sputtering and/or the deposition of TiO2 or SiO2, yet this high heat load, caused by a high current density, effectively eliminates polyethylene as a suitable substrate for many intended high power applications. Compounding the problem, if the heat load in the currently-available sputtering systems is lowered to a level that does not melt or otherwise render the polyethylene unsuitable, e.g., by reducing the power applied, the deposition rate is lowered to a point that results in a low-quality deposited layer and/or increases the required time for sputtering to a point that renders the use of polyethylene as a substrate infeasible from a commercial perspective.
There therefore remains a need for a device that provides improved sputtering deposition rates at a lower heat load.